1. Field of the Invention
The present invention relates to masks employed in photolithography processes used to make microelectronic components and, in particular, to a phase shift mask for such photolithography.
2. Description of Related Art
In producing microelectronic contacts and wiring on wafers using photolithographic processes, a major concern is how to print the smallest lines onto the wafer using optics.
Chrome or other light blocking materials used on masks have limitations at the line width where conventional resolution is lost, and may not be used below these line widths, presently about 0.2 microns. Moreover, the masks are sensitive to defects therein.
Phase shift masks have been well known wherein etching and/or additive methods have been used to impart a phase shift to light passing through the mask, for example, in U.S. Pat. Nos. 5,342,713 and 5,549,995. However, such phase shift masks have not been used to create images without use of chrome or other blocking material.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a photolithographic mask which has improved capability to produce printable images at or below the limit of optical resolution of the photolithographic process.
It is another object of the present invention to provide a photolithographic mask which is not subject to the limitations of imaging conventional chrome blocking layers.
A further object of the invention is to provide a simplified phase shift mask and method of making such mask which is less sensitive to mask defects.
It is yet another object of the present invention to provide a photolithographic mask which is of simpler design.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.